In computing, virtualization refers to the abstraction of computer resources. One useful definition is a technique for hiding the physical characteristics of computing resources from the way in which other systems, applications, or end users interact with those resources. This includes making a single physical resource (such as a server, an operating system, an application, or storage device) appear to function as multiple logical resources; or it can include making multiple physical resources (such as storage devices or servers) appear as a single logical resource. It can also include making one physical resource to appear, with somewhat different characteristics, as one logical resource.
A logical partition, commonly called an LPAR, is a subset of a computer's hardware resources, virtualized as a separate computer. In effect, a physical machine can be partitioned into multiple LPARs, each housing a separate operating system.
Logical partitioning is performed mostly on the hardware layer. For example, two LPARs may access memory from a common memory chip, provided that the ranges of addresses directly accessible to each do not overlap. One partition may indirectly control memory of a second partition, but only by commanding a process of the second partition to directly operate on the memory.
In the past, each CPU was dedicated to a single LPAR, but with the introduction of micro-partitioning, one CPU can be shared between separate LPARs. Micro-partitioning is a form of logical partitioning, and more specifically, micro-partitions are dynamic logical partitions (DLPARs) which run in the shared processor pool (SPP) and which share physical processors rather than have them dedicated. Dynamic logical partitioning is a capability of an LPAR to be reconfigured dynamically without shutting it down. Dynamic logical partitioning enables, e.g., memory, CPU capacity, and I/O interfaces to be moved between LPARs. The SPP can support up to ten times as many operating system images as there are physical processors. Also, there is no binding between OS images and physical processors; instead, e.g., a Hypervisor™ allocates processing resources according to scheduling rules defined when creating the partition. (Hypervisor is a trademark of International Business Machines Corporation in the United States, other countries, or both.) That is, for example, the Hypervisor (or a virtual machine monitor) is a virtualization platform that allows multiple operating systems to run on a host computer at the same time. Additionally, the Hypervisor is a function of the system firmware and may be present on servers whether partitioning is being used or not.
With the advent of computer logical partitioning and virtualization technology it is possible to use computer equipment in a much more efficient and cost effective manner than has been attainable in the past. It is now possible to have a single physical server partitioned into multiple logical servers, each of which appears to applications, users, and administrators as a physical stand-alone computer. Using technology such as IBM® Virtual I/O Server (VIOS), it is further possible to represent physical devices such as network adapters and disks as a collection of logical devices within each logical partition. (IBM is a registered trademark of International Business Machines Corporation in the United States, other countries, or both.)
Additionally, both logical and physical resources on IBM System p™ servers and partitions can be dynamically added, deleted, and moved within the hosting physical server. (System p is a trademark of International Business Machines Corporation in the United States, other countries, or both.) Another consideration is that servers, such as IBM System p, are often purchased with IBM Capacity Upgrade on Demand (CUoD), whereby, excess capacity such as CPU and memory is built into the physical server, but is not active until the client decides to enable them, e.g., either automatically or manually. CUoD allows for much quicker upgrades because the processors are already present on the server in an inactive state. In order to activate CUoD, a user may either rent, lease or buy the CUoD from, e.g., a service provider. Finally, with the introduction of IBM POWER6™ technology, it is possible for the first time to move live UNIX® applications and workloads between physical servers with no outage or interruption of service. (POWER6 is a trademark of International Business Machines Corporation in the United States, other countries, or both. UNIX is a registered trademark of The Open Group in the United States and other countries.) With all of these powerful features available, however, there does not yet exist a system and method to maximize cost avoidance through intelligent and automated workload relocation in virtualized environments.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.